Dana Petroleum shares rose after the energy exploration company said it had made a "significant" gas discovery in the North Sea.

The stock added 15p to £12.84 in morning trading.

"Preliminary analysis indicates that the reserves discovered are in-line with pre-drill estimates of approximately 130bn cubic feet of gas," the company said.

The company is also drilling the Bamboo prospect in the offshore Nile Delta, a well in the Dutch sector of the North Sea, and has just begun drilling at another well in the onshore Gulf of Suez, it said.

Stocks were mixed today, with the FTSE 100 down 8.3 points at 5787. Cruise operator Carnival was the index biggest gainer after Morgan Stanley lifted its target price to £32, from £27. "We see tremendous potential in Europe, where the source market will generate nearly half of Carnival's profit this year and demand actually grew 6% last year," the broker said. The shares gained 1.9% to £26.89.

Banks, including Royal Bank of Scotland and HSBC, also gained on the back of strong profits from US investment bank JP Morgan yesterday. RBS added 1.4% to 45.56p, while HSBC rose 1.1% to 700p.